The presence of blood in biological samples may be indicative of a serious medical problem, such as an internal injury or disease. As such, various testing procedures have been developed to test for the presence of blood, and in particular to test for hidden (occult) blood in biological samples. For example, blood that is present in a patient's stool may be the result of injury or disease at any point along the digestive tract, and may be indicative of anything from a minor perforation in the digestive tract lining to serious colorectal disease such as colon cancer. Early detection of occult blood is critical, as it is often the first, and may be the only, symptom of such injury or disease.
Various noninvasive tests have been developed to detect the presence of occult blood in biological material, such as stool. For example, typical fecal occult blood tests include guaiac smear tests (sold as Hemoccult®, Seracult®, Instaccult®, and Coloscreen®), and flushable reagent pads (sold as EZ DetectT® and ColoCARE®). While generally accurate, both types of tests have various disadvantages.
Diagnostically, guaiac smear tests are favored for colon cancer screening due to their established clinical use, because the results are generally interpreted by a medical professional (who is trained to determine false positive and false negative results), and because the medical professional is best able to advise and further test/treat the patient in the event of a positive test result, and ensure patient compliance with needed follow-up care. The use of such tests is well-described in the medical literature (See, for example, Greegor, D. H., (1969) Cancer 19; 330-337; Hastings, J. B., (1974) Amer. J. Surg. 127:228-233). In general, these tests involve placing a fecal sample on an absorbent paper coated with guaiac and adding a developer reagent containing hydrogen peroxide. If hemoglobin is present, the guaiac is oxidized, turning the paper blue.
In the event of a positive test result, the medical professional may perform a sigmoidoscopy to observe the rectum and lower colon for abnormalities, a colonoscopy to thoroughly observe the rectum and entire colon, and/or a barium enema followed by a series of x-rays to view abnormalities in the colon and rectum. However, the need that such tests generally be performed during medical visits results in relatively infrequent testing, and, as such, an injury or disease may go undetected and consequently untreated for a relatively long period of time. As such, they are not necessarily well-suited for the early detection of colorectal problems.
Further, while such tests may be prescribed to patients for in-home use, this is generally not favored due to the stool handling and procedural requirements needed to ensure that the test is properly performed, which also results in relatively poor patient compliance, and, in the event of a positive test result, requires the patient to visit the doctor in order to obtain further necessary testing and/or treatment, increasing the likelihood that certain patients will not receive such further medical care. Some medical professionals also question whether such tests should be relied on for the screening of colorectal cancer (see in this regard, for example, H. Bleiberg, Annals of Oncology (2002) 13:44-46).
Flushable reagent pads, on the other hand, are more suitable for in-home use, as they are generally available without a prescription and do not require direct stool handling or laboratory processing. However, they have certain disadvantages, including that they are not preferred diagnostically because they rely on the dispersal of occult blood in the toilet to ensure a reaction with the developer (and at the threshold sensitivities), and must be viewed in (or removed from) the toilet bowl to determine the test results. Furthermore, they have only been on the market for a relatively short time.
Various attempts have been made to develop alternative examination devices that afford certain of the diagnostic and compliance benefits of the aforementioned tests, but such devices have various disadvantages rendering them clinically and/or otherwise unsuitable. In this regard, for example, U.S. Pat. No. 4,473,079 discloses an examination glove having an indicator impregnated in a filter pad at the base of the thumb, and a solid peroxide compound dispersed in a spreadable material at the tip of the thumb. In use, a stool sample is obtained at the index finger, coverings on each of the dispersed peroxide and indicator compounds are removed by the patient using his alternate hand, the stool sample is contacted with the peroxide compound, and this mixture is then rubbed onto the indicator-impregnated filter paper at the base of the thumb. However, such devices as those described in the aforementioned '079 patent include numerous drawbacks that render them unsuitable for clinical use, including, for example, the need for specialized peroxide preparations, the availability of the chemicals to react with the ambient environment, the need for two-handed operation, and their general unsuitability for use by certain patients (for example, patients suffering from arthritic conditions cannot use such devices as, in use, the fingers must be bent to a significant degree in order to carry out the procedure).